Microbeam irradiators can be utilized for studying the microscopic biological effects of radiation in the cellular and sub-cellular level. Such devices can be utilized to bombard one or more cells with charged particles or photons for predetermined radiation dose and dose rate. An understanding of radiobiology at the cellular and sub-cellular level is important for improvements of cancer treatment and for an understanding of low dose radiation risk. Cellular micro-radiation is recognized as a powerful technique for this endeavor. One of the most active areas of research using a microbeam irradiator is the “bystander effect”, which involves the response of “unhit” cells to the radiation deposited in their neighboring cells. “Bystander effect” studies using microbeam devices have revealed the complicated intra-cellular and inter-cellular response to radiation that may have significant impact on the policy making of radiation protection for general public and for the space program.
Cell irradiation can include exposing cells to alpha particles, electrons, or X-rays. Recently, there has been interest in low-linear energy transfer (LET) microbeams using electrons and ultrasoft X-rays. Thermionic emission and field emission are two mechanisms for generating electrons. Although field emission is a sometimes preferred mechanism to extract electrons, many currently available vacuum electronic devices utilize thermionic electron sources. The wide use of thermionic electron sources may be partly due to the lack of effective electron field emitters. Recent studies have shown that carbon nanotubes have promising electron emission properties with high emission current, low turn-on field, and lifetime that can be required for device applications. A typical field emission device can include a cathode having a plurality of electron field emitters (e.g., carbon nanotubes) and an anode spaced from the cathode. A voltage applied between the anode and the cathode can induce the emission of electrons from the electron field emitters towards the anode.
A few large research institutions in the world are capable of delivering microbeam irradiation at the cellular level. These microbeam devices require major resources to develop and maintain. Further, in currently available microbeam irradiators, there is only a single microbeam port. One exemplary single port electron microbeam having a thermionic electron source includes an electron gun consisting of a heated filament and electron optics for accelerating and collimating a broad electron beam. The electron optics includes a suppression aperture that allows pulsing of the beam with sub-microsecond time resolution. The final spatial resolution of an electron microbeam can be achieved either by focusing or collimation. The electron microbeam can be used to target individual cells without significant scattering to neighboring cells. Target cells or sub-cellular regions designated for irradiation in a population must be irradiated one at a time by physically aligning the microbeam with each of the target cells. Some research experiments require the irradiation of a large number of individually selected cells, as many as 10,000, to obtain statistically significant results. This requirement makes it difficult to utilize single port microbeam devices for experiments requiring irradiation of a large number of cells and, especially, if real-time observation is also required.
Most cell irradiations in research labs today use irradiators that cannot deliver radiation beams much smaller than a centimeter. Therefore, researchers often have to deduce conclusions about microscale activities of a cell from macroscopic studies of irradiating a group of cells. The lack of microscale radiation manipulation ability can be especially detrimental when studying a minority cell type in a large cell population because of the low signal to noise ratio in the experimental data.
Accordingly, in light of desired improvements associated with microbeam cellular irradiators, there exists a need for improved microbeam irradiator functionality and availability and related methods.